Insulating bushing for electrical apparatus



July 27, 1937.

E. E. ARNOLD ET AL INSULATING BUSHING FOR ELECTRICAL APPARATUS WITNESSES bad Eigtl.

Filed March 29, 1954 INVENTORS Edwin E/Irno/afana GOI'BQYIOU A. Bur/r Patented July 27, 1937 UNITED STATES PATENT OFFICE INSULATING BUSHING FOR ELECTRICAL APPARATUS sylvania Application March 29, 1934, Serial No. 717,981

5 Claims.

Our invention relates to bushings for electrical apparatus, and more particularly to condenser bushings such as are usually employed in connection with high voltage electrical apparatus such as circuit breakers and transformers.

When circuit breakers and transformers are disposed in tanks or cases filled with oil or some other fluid insulating medium, the high voltage leads therefrom are usually brought out through the tops or covers and bushings embodying dielectric and metal elements are used to support the leads and insulate them from the covers at the points where they pass through the covers. Under such circumstances, it is necessary to support the bushings approximately midway of their ends by some means engaging the tops of the tanks. Usually the bushing is supported in the cover by an engaging means comprising a metallic collar which passes around the central part of the bushing and is provided with a flange that may be secured to the cover.

Inasmuch as the collar is of metal and the outer portion of the bushing is of dielectric material, it is usually difficult to secure a good fluid tight engagement between the dielectric portion of the bushing and the supporting collar, particularly when the bushings are large in diameter. Also, the influence of air, gases, oil and electrical and mechanical stresses often adversely affects the joints between the collars and the bushings.

Therefore, it is an object of our invention to provide for so surrounding a supporting collar to a condenser bushing that the joint between them will be. permanently fluid tight and will be unaffected by the surrounding air or gases, the fluid insulating medium in the tank or by any electrical or mechanical stresses to which it may be subjected.

It is also an object of our invention to provide a bushing and support therefor which shall be simple and durable in construction, economical to manufacture and install and effective in operation.

Another object of our invention is to provide a bushing and supporting collar which may be pressed into a holding engagement with each other without the necessity of providing a plurality of additional holding parts.

A further object of our invention is to provide a bushing and a supporting collar therefor which may be pressed together in such manner that any sealing and insulating compound used between the collar and the bushing will be caused to impregnate and penetrate the joints and surfaces at the junction of the collar and bushing by hydrostatic pressure raised by Virtue of a contracting space during the operation of pressing together the collar and the bushing.

Another object of our invention is to provide a bushing and a collar structure in which any sealing and insulating compound used at the junction of the collar and the bushing will lubricate the meeting parts While they are being pressed together and will not only assist in positioning the collar on. the bushing, but will ultimately harden and set to hold the parts in place.

For a better understanding of our invention, reference may be had to the accompanying drawing, in which:

Figure 1 is a view, in, front elevation, of a condenser bushing provided with a supporting collar in accordance with our invention;

Fig. 2 is an enlarged elevational View partly in section of the central portion of the bushing disclosed in Fig. l and showing the supporting collar ready to be pressed into its flnal position; and

Fig. 3 is a view similar to Fig. 2 but showing the collar pressed downwardly into its final position.

Referring more particularly to the drawing, we have illustrated an insulating device or bushing structure comprising a condenser bushing I and a supporting collar 2 provided with a supporting flange 3. The flange 3 is provided with a plurality of suitable bolt holes 4 by means of which the structure may be securely bolted to the cover or top of the tank (not shown) with which it is associated. The bushing 2 is preferably in the form of an elongated and stepped tube of the condenser type such as is composed of a plu rality of alternating layers of insulating and conducting materials wound on a conductor 5.

The conductor 5 is preferably a copper rod or tube, although it may be of any other metal suitable for a high voltage conductor, and its end portions may be connected in any suitable manner to the electrical apparatus (not shown) with which it may be associated.

In practicing our invention, the bushing is prepared to receive the collar 2 by so molding it or turning it in a lathe that its middle portion is provided with an annular sealing shoulder 6, an annular sealing portion 1 of less diameter than the shoulder 6, an annular spacing portion 8 of less diameter than the sealing portion 1, an annular locking groove 9 of less diameter than the spacing portion 8, and an annular collar-guiding portion IEI of greater diameter than the groove 9 but of less diameter than the spacing portion 8.

In order that the cooperating collar 2 may be pressed upon the middle portion oi the bushing just described, the inner portion of the collar is machined or otherwise conditioned to provide an annular shoulder I I at its lower end, an annular spacing portion I2, an annular shoulder I3, an annular sealing portion I4 and, at its upper end, an annular upwardly bevelled locking portion l5.

As shown in the drawing, the diameter A of the guiding portion II) of the bushing is slightly less than the diameter B of the sealing portion I4 of the collar to permit the collar to slide down over the upper part of the bushing into position to be forced into its final place on the bushing. The diameter B of the sealing portion I4 of the collar is slightly less than the diameter D of the spacing portion 8 of the bushing to cause a press fit between these two parts when the collar is pressed into its final position on the bushing. The diameter E of the spacing portion I2 of the collaris also slightly less than the diameter F of the sealing portion I of the bushing to cause a press fit between these two parts when the collar is forced into its final position on the bushing.

The diameter D of the spacing portion 8 of the bushing is somewhat less than the diameter E of the spacing wall I2 of the collar to provide a thin annular space or chamber for receiving a suitable sealing fluid-like compound or gum such as a heavy shellac. The distance between the spacing wall 8 and the spacing wall I2 is preferably very small say, from inch to A; inch depending upon the size of the bushings; that is, the annular chamber should be very thin but its longitudinal length should be several inches, as is indicated by the drawing.

The diameter C of the inner portion of the locking groove 9 in the bushing is considerably less than the diameter of the bevelled portion I5 of the collar to provide a space for receiving a suitable sealing and locking medium H as shown in Fig. 3.

In assembling the collar and the insulator, we first paint or smear the middle portion of the bushing and the interior of the collar with a suitable sealing gum or heavy shellac I9. Then, the collar is placed over the upper end of the bushing and moved down until its shoulder II impinges against the shoulder Ia on the bushing. After this, the parts are placed in a suitable press and pressure is applied until the collar is moved downwardly on the bushing from the position shown in Fig. 2 to its final position as shown in Fig. 3.

In the final position, the shoulder II on the lower end of the collar engages the shoulder 6 on the bushing and the lower portion of the spacing wall I2 engages the sealing portion "I of the bushing in what is known as a press fit. Similarly, the sealing portion I4 on the upper end of the collar engages the upper portion of the spacing portion fl of the bushing to provide a press fit between the collar and the bushing at the upper end thereof. In pressing the collar on the bushing, the sealing shoulder II is moved downwardly and thereby applies a hydrostatic pressure to the sealing gum I9 trapped within the space defined by the shoulders II and I3 and the walls 8 and I2. This hydrostatic pressure causes the insulating gum to fill and penetrate the joints and surfaces and thereby adds to the insulating efiectiveness of the gum. Furthermore, inasmuch as the engagement of the lower end of the collar spacing wall I2 with the sealing portion 1 of the bushing is a press tight fit and the engagement of the sealing portion I4 of the collar with the upper end of the spacing wall 8 of the bushing is also a press fit, the insulating gum is thereby disposed in a closed chamber and thus protected from any deteriorating action by the oil or insulating medium in the tank or by the air or any other external means.

Upon the collar being seated in its final position upon the bushing, the excess gum is wiped oil and a suitable sealing and locking medium such as a lead alloy is melted and poured into the space formed by the position of the bevelled locking portion i5 adjacent to the locking groove ti and is permitted to cool harden therein. The hardened locking ring only prevents the collar .2 on the bushing but also acts as an additional sealing means for preventing the entrance of any deleterious substance into the joint between the ring and the bushing.

In View of the foregoing description and il1us-- tration, it is seen that we have provided a simple and durable bushing structure comprising only a very few parts and not requiring bolts, rivets or similar devices to hold them in operative position and that the structure may be easily and economically manufactured, assembled and installed.

Although we have described only one specific from working loose embodiment of our invention, it is to be under- I! stood that changes therein and modifications thereof may be made without departing from the spirit and scope of our invention.

We claim as our invention:

1. A bushing device comprising a bushing having an annular shoulder and an annular spacing portion on its exterior surface, a fluid-lilre insu-- lating medium disposed on the annular spacing portion of the bushing, a supporting collar disposed on the bushing, said collar having on its internal surface a spacing portion and a shoulder, the shoulder being on the end of the spacing portion opposite the shoulder on the spacing portion of the bushing, whereby a pressing together of the collar and the bushing will cause the shoulder and the spacing portions to cooperatively compress the fluid-like insulating medium into a compact mass in the closed chamber formed by the spacing portions and the shoulders of the bushing and the collar.

A bushing device comprising a bushing having an annular shoulder and an annular spacing portion on its exterior surface, a fluid-like insulating medium disposed on the annular spacing portion of the bushing, a supporting collar disposed on the bushing, said collar having on its internal surface a spacing portion and a shoulder, the shoulder being on the end of the spacing portion opposite the shoulder on the spacing portion of the bushing, whereby a pressing together of the collar on the bushing will. cause the shoulder and the spacing portions to cooperatively compress the fluid-like insulating medium into a compact mass in the closed chamber formed by the spacing portions and the shoulders of the bushing and the collar, and means for locking the collar in its pressed position on the bushing.

3. A bushing device comprising a bushing having an annular shoulder and an annular spacing portion on its exterior surface, a fluid-like insulating medium disposed on the annular spacing portion of the bushing, a supporting collar dis-- posed on the bushing, said collar having on its internal surface, a spacing portion and a shoulder, the shoulder being on the end of the spacing perof lead alloy ll not 7- tion opposite the shoulder on the spacing portion of the bushing, whereby a pressing together of the collar on the bushing will cause the shoulder and the spacing portions to cooperatively compress the fiuid-like insulating medium into a com-- pact mass in the closed chamber formed by the spacing portions and the shoulders of the bushing and the collar, and an annular locking ring disposed in cooperating grooves in the bushing and the collar to lock said collar in Working position on the bushing.

4. An elongated cylindrical bushing having a supporting collar surrounding a portion thereof, means for securing said collar to the bushing comprising an annular shoulder proportioned to abut one end of the collar and adjacent areas of successively decreasing diameters, and an annular area on the inner face of the collar adjacent to the other end thereof, the diameters of said areas and the inner diameters of the collar being such that when the collar is pressed telescopically on the bushing against the shoulder thereof areas at both ends of the collar tightly fit areas on said bushing leaving an enclosed annular space therebetween, and an annular seal between the smallest of said successively reduced bushing areas and the edge of the collar remote from the annular shoulder on said bushing.

5. A bushing support comprising an elongated cylindrical bushing having a plurality of areas of successively decreasing diameters in one direction, a supporting collar therefor having areas of successively increasing diameters in the same direction to telescopically engage the bushing areas in a press-fit relation, an intermediate area on said bushing being of less diameter than the collar area opposite to it to define an annular chamber therebetween, and an insulating medium completely filling said chamber and compressed therein by said telescopic engagement.

EDWIN E. ARNOLD. GORDON A. BURR. 

